Interspinous process implants having deployable engagement arms

ABSTRACT

Spinal implants include an elongated body portion dimensioned and configured for percutaneous introduction into a target interspinous process space, at which interspinous distraction and/or spinal fusion are desired. The body portion can include a threaded outer surface, or alternatively a smooth surface. The body portion can include one or more interior cavities, and can include deployable engagement members adapted and configured to move in tandem between a stowed position retracted within the interior cavity of the body portion and a deployed position extended from the interior cavity of the body for engaging adjacent spinous processes. An internal drive assembly for selectively moving the engagement members from the stowed position to the deployed position can be provided, as can a elements for locking the engagement members in a deployed position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of, and claimsthe benefit of priority to U.S. patent application Ser. No. 12/011,905,filed Jan. 30, 2008, which in-turn claims priority to U.S. PatentApplication Ser. No. 61/001,430, filed Nov. 1, 2007, U.S. PatentApplication Ser. No. 61/000,831, filed Oct. 29, 2007, U.S. PatentApplication Ser. No. 60/961,780, filed Jul. 24, 2007, U.S. PatentApplication Ser. No. 60/959,799, filed Jul. 16, 2007, and U.S. PatentApplication Ser. No. 61/007,916, filed May 1, 2007. This applicationalso claims the benefit of priority to U.S. Patent Application Ser. No.61/207,339, filed Feb. 11, 2009. Each of the aforementioned patentapplications is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject invention is directed to spinal implants, and moreparticularly, to an interspinous process implant with a threaded bodyand deployable engagement arms for percutaneous placement in theinterspinous process space to treat lumbar spinal stenosis.

2. Description of Related Art

The spine consists of a column of twenty-four vertebrae that extend fromthe skull to the hips. Discs of soft tissue are disposed betweenadjacent vertebrae. The vertebrae provide support for the head and body,while the discs act as cushions. In addition, the spine encloses andprotects the spinal cord, which is surrounded by a bony channel calledthe spinal canal. There is normally a space between the spinal cord andthe borders of the spinal canal so that the spinal cord and the nervesassociated therewith are not pinched.

Over time, the ligaments and bone that surround the spinal canal canthicken and harden, resulting in a narrowing of the spinal canal andcompression of the spinal cord or nerve roots. This condition is calledspinal stenosis, which results in pain and numbness in the back andlegs, weakness and/or a loss of balance. These symptoms often increaseafter walking or standing for a period of time.

There are number of non-surgical treatments of stenosis. These includenon-steroidal anti-inflammatory drugs to reduce the swelling and pain,and corticosteroid injections to reduce swelling and treat acute pain.While some patients may experience relief from symptoms of spinalstenosis with such treatments, many do not, and thus turn to surgicaltreatment. The most common surgical procedure for treating spinalstenosis is decompressive laminectomy, which involves removal of partsof the vertebrae. The goal of the procedure is to relieve pressure onthe spinal cord and nerves by increasing the area of the spinal canal.

Interspinous process decompression (IPD) is a less invasive surgicalprocedure for treating spinal stenosis. With IPD surgery, there is noremoval of bone or soft tissue. Instead, an implant or spacer device ispositioned behind the spinal cord or nerves between the spinousprocesses that protrude from the vertebrae in the lower back. Awell-known implant used for performing IPD surgery is the X-STOP®device, which was first introduced by St. Francis Medical Technologies,Inc. of Alameda Calif. However, implantation of the X-STOP® device stillrequires an incision to access the spinal column to deploy the X-STOP®device.

It would be advantageous to provide an implant for performing IPDprocedures that could be percutaneously inserted into the interspinousprocess space and effectively treat lumbar spinal stenosis.

SUMMARY OF THE INVENTION

The subject invention is directed to a new and useful spinal implantthat includes, in one aspect, a spinal implant comprising: an elongateddimensioned and configured for percutaneous introduction into theinterspinous process space. The body portion can be fully or partiallythreaded, or alternatively have a smooth surface.

The body portion can include an interior cavity, and further comprisesdeployable engagement members adapted and configured to move in tandembetween a stowed position retracted within the interior cavity of thebody portion and a deployed position extended from the interior cavityof the body for engaging the spinous process.

A drive assembly can be provided, extending into the interior cavity ofthe threaded body portion for selectively moving the engagement membersin tandem from the stowed position to the deployed position. Means forselectively locking the engagement members in the deployed position,operatively associated with the drive assembly, can be provided. Thedrive assembly can include a main drive shaft that extends into theinterior cavity of the body portion along the longitudinal axis of thebody portion. The drive shaft can include a transmission end having aplurality of beveled gear teeth for operatively meshing with the beveledgear teeth on the central hubs of each engagement member to facilitatethe transmission of torque therebetween.

Two engagement members can be provided for engaging the spinous process,wherein each engagement member includes a pair of curved engagement armsextending radially outwardly from a central hub. The central hub of eachengagement member can include a plurality of beveled gear teeth and bemounted for rotation about a common shaft extending transverse to thelongitudinal axis of the body portion. Each engagement arm can include adistal claw portion having a plurality of dissimilar teeth for engagingthe spinous process.

In accordance with the invention, a threaded body portion can include anouter profile, tapering axially inwardly in a distal nose portionthereof, configured to gradually distract adjacent spinous processesduring insertion, or advancement, of the implant into the interspinousprocess space. Threads can be provided on the body portion, and canextend at least partially over the nose portion thereof. The distal noseportion can taper axially inwardly with respect to a central region ofthe body, by an angle of between about 5 degrees and 65 degrees, withrespect to a longitudinal axis thereof. In accordance with one aspect ofthe invention, this angle can be between about 15 and 45 degrees. Inaccordance with another aspect, this angle can be between about 25 and35 degrees. In accordance with another aspect, this angle can be about30 degrees.

An interior core portion adapted and configured for rigidifying thespinal implant can be provided and arranged within the body portion ofthe subject implants. Such core portions can include an integral tipportion, arranged at the distal end of the implant. If desired, aseparately formed tip portion can be provided and arranged at the distalend of the implant, with or without such a core portion.

In accordance with the invention, the body portion and the tip portioncan be formed of dissimilar materials.

The tip portion can include an axially inward taper, and can be providedwith or without threads on the outer surface thereof, depending on theprecise implementation.

The body portion can include a separately formed proximal portion,formed of a material dissimilar from a material from which a centralportion of the body portion is formed. The proximal portion can beformed of a metal material, and the central portion of the body portioncan be formed of a polymeric material, for example.

At least one detent can be provided on the implant for aligning theimplant with an insertion device therefor.

In accordance with another aspect of the invention, a spinal implantincludes an elongated body portion dimensioned and configured forpercutaneous introduction into the interspinous process space and havingan interior cavity, deployable engagement members adapted and configuredto move in tandem between a stowed position retracted within theinterior cavity of the body portion and a deployed position extendedfrom the interior cavity of the body for engaging the spinous process,and a rotatable drive shaft extending into the interior cavity of thethreaded body portion along the longitudinal axis thereof forselectively moving the engagement members in tandem from the stowedposition to the deployed position.

A locking cap can be provided, operatively associated with the rotatabledrive shaft and the body portion for selectively locking the engagementmembers in the deployed position.

Two engagement members can be provided for engaging the spinous process,wherein each engagement member includes a pair of curved engagement armsextending radially outwardly from a central hub. The central hub of eachengagement member can include a plurality of beveled gear teeth and ismounted for rotation about a common shaft extending transverse to thelongitudinal axis of the body portion.

A drive shaft can be provided, including a transmission end having aplurality of beveled gear teeth for operatively meshing with the beveledgear teeth on the central hubs of each engagement member to facilitatethe transmission of torque therebetween. Each engagement arm can includea distal claw portion having a plurality of dissimilar teeth forengaging the spinous process.

In accordance with still another aspect of the invention, a method oflateral insertion of a spinal implant into an interspinous process spaceis provided, comprising the steps of forming an incision in a patient'sskin, lateral from a target interspinous process space, in which theimplant is to be placed, inserting a stylet through the incision,laterally to the target interspinous process space, using an internalimaging technique, to form an entry path, inserting one or moredilators, sequentially, along the entry path to dilate soft tissuesbetween the incision and the target interspinous process space,inserting a sleeve through the entry path, selecting an implant having asize appropriate for a desired amount of interspinous distraction,inserting the implant, held by an insertion device, through the sleeve,up to the target interspinous process space, and advancing the implantinto the interspinous process space.

Methods in accordance with the invention can further include thefollowing steps, for example. Such methods can further include a step ofaligning the implant with spinous processes of the patient following theadvancing step.

The advancing step can include rotating the implant along a longitudinalaxis thereof, to effect axial advancement of the implant by way ofthreads formed on an outer surface thereof.

Such methods can further include a step of deploying engagement members,when the implant includes a plurality of engagement members for engagingadjacent spinous processes to the target interspinous process space.

Fluoroscopy can be used as an internal imaging technique duringinsertion of the stylet and optionally throughout the procedure, such asduring insertion of the implant itself.

A tap can be inserted into the target interspinous process space, andused to form threads on surfaces of adjacent spinous processes, prior toinsertion of a threaded implant, for engagement with threads of theimplant.

Methods of the invention can further include the step of filling one ormore cavities in the implant with an osteogenesis promoting substance.The osteogenesis promoting substance can be, for example, demineralizedbone gel.

It is to be understood that each feature of the disclosed implants andrelated methods may be interchanged and coupled freely with the variousother features to utilize any combination thereof. These and otherfeatures of the interspinous implant and percutaneous placement methodof the subject invention will become more readily apparent to thoseskilled in the art from the following detailed description of thepreferred embodiment taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject inventionappertains will readily understand how to make and use the interspinousimplant of the subject invention without undue experimentation,preferred embodiments thereof will be described in detail herein belowwith reference to certain figures, wherein:

FIG. 1 is a perspective view of an interspinous implant constructed inaccordance with a preferred embodiment of the subject invention, whichincludes a threaded body portion (shown in phantom view) dimensioned andconfigured for percutaneous introduction into the interspinous processspace of a patient and a set of engagement arms for selectively engagingthe spinous process, the engagement arms being disposed in a stowedposition within the interior cavity of the threaded body portion;

FIG. 2 is a perspective view of the interspinous implant of FIG. 1, withthe engagement arms disposed in a deployed position extending from theinterior cavity of the threaded body portion;

FIGS. 3, 4 and 5 are exploded perspective views of the interspinousimplant of the FIG. 1, with parts separated for ease of illustration;

FIG. 6 is a detail cross-sectional view of a proximal end portion of theinterspinous implant of the FIG. 1, taken along line 6-6 of FIG. 1;

FIG. 7 is a transverse cross-sectional view, as seen facing the proximalend of the interspinous implant of the FIG. 1, taken along line 7-7 ofFIG. 6;

FIG. 8 is a representational view illustrating a dorsal insertiontechnique, illustrated with the interspinous implant of the FIG. 1,applicable to all embodiments of the invention;

FIG. 9 is a representational view illustrating a lateral insertiontechnique, illustrated with the interspinous implant of the FIG. 1,applicable to all embodiments of the invention;

FIG. 10 is a rear (dorsal side) representational view, illustratingadvancement of the interspinous implant of the FIG. 1, applicable to allembodiments of the invention;

FIG. 11 is a rear (dorsal side) representational view, illustrating theinterspinous implant of the FIG. 1, having engagement arms deployed,engaging adjacent spinous processes;

FIG. 12 is a perspective view of a further embodiment of an interspinousimplant in accordance with the invention, having an integral tap chamferon a leading end thereof, providing self-tapping capability, eliminatinga need to separately tap an interspinous process space;

FIG. 13 is a partial lower perspective view of the interspinous implantof FIG. 12;

FIG. 14 is a perspective view of a further embodiment of an interspinousimplant in accordance with the invention, having a separately formed tipportion and internal core (FIG. 15), for additional structural rigidity;

FIG. 15 is an exploded view of the interspinous implant of FIG. 14;

FIG. 16 is a perspective view of a further embodiment of an interspinousimplant in accordance with the invention, having an outer surface thatis not threaded;

FIG. 17 is a rear (dorsal) view illustrating placement of theinterspinous implant of FIG. 16, placed in a target interspinous processspace; and

FIG. 18 is a partial exploded view of an alternative arrangement for adistal tip portion for interspinous implants in accordance with theinvention.

DETAILED DESCRIPTION

Referring now FIG. 1, there is illustrated one exemplary embodiment ofan interspinous implant constructed in accordance with a preferredembodiment of the subject invention and designated generally byreference numeral 10. Implant 10 is particularly well adapted for use inperforming minimally invasive surgical procedures for treating spinalstenosis, including, for example, interspinous process decompression(IPD).

It is envisioned however, that the implant 10 of the subject inventioncan be used in other spinal procedures as well, including, but notlimited to as an adjunct to spinal fusion procedures, or as a spinalstabilization device. Those skilled in the art will readily appreciatefrom the following description that the interspinous process implant ofthe subject invention is well adapted for percutaneous insertion, andthus overcomes many of the deficiencies of prior art devices presentlyused in IPD procedures. That is, the implant 10 is dimensioned andconfigured for introduction and placement through a small skin incisionrather than in an open surgical procedure involving a cut down oftissue.

Referring to FIGS. 1 through 5, the interspinous implant 10 of thesubject invention includes a threaded body portion 12 having right andleft body sections 12 a, 12 b. The body sections 12 a, 12 b are heldtogether in part by a securement pin 14 located adjacent the taperednose cone 15 of the implant body 12.

The two body sections 12 a, 12 b are preferably formed from abiocompatible polymeric material that has a modulus of elasticity thatis substantially similar to that of bone, for example,polyaryletheretherketone thermoplastic (PEEK) or a similar material.However, the body sections could also be made from machined bone, from abiocompatible metal such as, for example, a titanium alloy or stainlesssteel, a ceramic, a composite or a like material or combination thereof.

The body portion 12 is dimensioned and configured for threaded placementbetween the spinous processes of symptomatic disc levels. In thisregard, it is envisioned that the outer diameter of the implant 10 canrange from about 8.0 mm to about 16.0 mm, with the thread depth beingabout 1.0 mm. The threads on the body portion 12 of the implant 10 canbe configured so that the implant is self-tapping to ease insertion ofthe implant into the interspinous process space, as described below inconnection with FIGS. 12 and 13.

In the embodiment illustrated in FIGS. 1-7, an optional detent 3, inthis embodiment composed of detents 3 a and 3 b, respectively formed inthe two body sections 12 a and 12 b, is provided for engaging aninsertion device in a bilateral insertion technique, in which insertiondevices are attached to both the proximal and distal ends of theimplant, engaging the detent 3. Such a technique is described in U.S.Patent Publication No. 2009/0054988, which is incorporated herein byreference in its entirety.

It is envisioned that implant 10 can have a variety of thread forms,such as, for example, cutting threads or box threads. It is alsoenvisioned that the body portion of the implant can be provided withoutthreads, while remaining well within the scope of the subjectdisclosure, and as discussed in more detail hereinbelow, in connectionwith FIGS. 16 and 17.

In addition to facilitating advancement of the implant 10 into a targetinterspinous process space through axial rotation, thereof, the threadson implant 10 also assist in spinal stabilization by engagingcorresponding threads that are formed prior to or during insertion, inthe adjacent spinous processes, as will be described in more detailhereinbelow.

Furthermore, as illustrated, the distal end portion of the implant 10includes a tapered nose portion 15, and therefore gradually dilates theinterspinous process space during insertion. Accordingly, a separatespreader is not required for dilating the interspinous process spaceprior to insertion of the implant 10. The distal nose portion 15, asillustrated, tapers axially inwardly with respect to a central region ofthe body, by an angle α (alpha) of between about 5 degrees and 65degrees, with respect to a longitudinal axis 19 thereof. In accordancewith one aspect of the invention, this angle α (alpha) can be betweenabout 15 and 45 degrees. In accordance with another aspect, this angle α(alpha) can be between about 25 and 35 degrees. In accordance withanother aspect, this angle can be about 30 degrees. It is to beunderstood, however, that the angle α (alpha) should not be limited tothe aforementioned ranges. Further, it is to be understood that theseranges can apply to other embodiments of the invention.

Moreover, being provided with such threads, the implant 10 can beemployed as a threaded fusion cage for the interspinous process space,as will be appreciated by those skilled in the art. To facilitateimplementation as a fusion cage, the body portion 12 can be providedwith several apertures or cutouts which allow for the insertion ofdemineralized bone or another type of fusion adjunct material, whichapertures also promote bone ingrowth, as will be discussed furtherbelow.

The body portion 12 of implant 10 defines an interior cavity 18 orchamber which houses two deployable engagement members 20 a, 20 b formedfrom titanium, stainless steel, ceramic, composite, or a similarhigh-strength, light-weight biocompatible metal. The engagement members20 a, 20 b are adapted and configured to move in tandem between a stowedposition retracted within the interior cavity 18 of the body portion 12,as shown in FIG. 1, and a deployed position extended from the interiorcavity 18 of the body portion 12, as shown in FIG. 2, for engaging thespinous processes. Advantageously, once the engagement members 20 a, 20b are deployed to engage the spinous processes, migration of the implant10 is inhibited, in addition to lateral migration resistance provided bythe threads alone.

As illustrated, and best seen in FIGS. 3-5, each engagement member 20 a,20 b includes a pair of curved engagement arms 22 a, 22 b that extendradially outwardly in an arcuate manner from a central hub 24. In theillustrated embodiments, each engagement arm 22 a, 22 b includes adistal claw portion 26 a, 26 b. The claw portions 26 a, 26 b of theengagement arms 22 a, 22 b are preferably each provided with a pluralityof sharpened teeth 28 for engaging and puncturing the bone of theadjacent spinous processes, to effect stabilization of the implant 10.The teeth 28 on each claw portion 26 a, 26 b are preferably, but notnecessarily, dissimilar in size and orientation, to better engage anindividual's particular anatomy, which may vary between patients in bothsize and shape.

The central hub 24 of each engagement member 20 a, 20 b includes aplurality of beveled gear teeth 30 and is mounted for rotation about aspindle shaft 32 extending transverse to the longitudinal axis of thebody portion 12. The spindle shaft 32 is secured in place within thebody portion 12 of implant 10 by a retaining ring 34, such as a nut,circlip, snap or press-fit ring or by other mechanical fastener known inthe art. In accordance with a preferred aspect, the ring 34, oralternatively a cap or termination having another suitable configurationis welded to the spindle shaft 32. In a preferred embodiment, thiswelding is accomplished by laser welding. In the embodiment of FIGS.1-5, the spindle shaft 32 and retaining ring 34 also serve to hold bodysection 12 a, 12 b together, in conjunction with a more proximallyarranged securement pin 14.

The interspinous implant 10 further includes an actuation assemblydefined in part by an elongated drive shaft 40 that extends into theinterior cavity 18 of the body portion 12 along the longitudinal axisthereof. The drive shaft 40 includes a proximal threaded section 42, amedial support flange 44 and a distal drive section 46. The proximalthreaded section 42 includes a hexagonal shaped end-fitting 48 forcooperating with an insertion device (not shown in FIGS. 1-5) having areceptacle for receiving at least the end-fitting 48 of the shaft 40.The insertion device is used to axially rotate or otherwise actuate thedrive shaft 40 to facilitate selective deployment of the engagementmembers 20 a, 20 b.

The medial support flange 44 of drive shaft 40 is accommodated within ajournal chamber 45 formed within the proximal end portion of theinterior cavity 18 of body portion 12, together with an annular bushing50 that supports the axial rotation of drive shaft 40. The distal drivesection 46 of drive shaft 40 includes a distal bevel gear 52 adapted andconfigured to operatively mesh with and transmit torque to the beveledgear teeth 30 on the central hub portion 24 of each engagement member 20a, 20 b to selectively rotate the engagement arms 22 a, 22 b of the twoengagement members 20 a, 20 b, in tandem, into a deployed position, asillustrated, for example in FIGS. 2 and 11.

A locking cap 60 is operatively associated with the threaded proximalsection 42 of drive shaft 40. Locking cap 60 serves two functions.First, locking cap 60 functions to hold body sections 12 a, 12 btogether, in conjunction with securement pin 14 and spindle shaft 32. Inaddition, locking cap 60 functions to selectively lock the pairedengagement arms 22 a, 22 b of engagement members 20 a, 20 b in adeployed position. More particularly, the locking cap 60 iscooperatively associated with a threaded lock nut 62 by way of a pair ofopposed set pins 64 a, 64 b which are captured within an annular channel66 formed in lock nut 62. Lock nut 62 is threadedly associated with thethreaded proximal section 42 of drive shaft 40.

In addition, locking cap 60 includes an interior planar surface 67, asbest seen in FIG. 5, having a set of four locking ribs 68 a-68 dprovided thereon. These ribs 68 a-68 d are dimensioned and configured tolockingly rotationally engage with a toothed annular surface 70 a, 70 b(see FIG. 3) provided on the proximal end of body portions 12 a, 12 b.The locking interaction of the ribs 68 a-68 d and toothed annularsurface 70 a, 70 b, best seen in FIGS. 1 and 2 through the semi-circularport 72 formed in the side wall of locking cap 60. The ports 72, whichcan be provided in one or more circumferentially opposed pairs, canfacilitate machining of internal features of the locking cap 60.

In use, once the engagement arms 22 a, 22 b of each engagement member 20a, 20 b have been deployed by axially rotating drive shaft 40, thelocking cap 60 is moved axially into a locking position by rotation ofthe threaded lock nut 62, until such time as the locking ribs 68 a-68 dof the locking cap 60 engage the toothed annular surface 70 a, 70 b onthe proximal end of body portions 12 a, 12 b. It should be noted thatalthough the engagement arms 22 a, 22 b are deployed in tandem, asembodied, the invention is not limited to such configuration.

As best seen in FIGS. 5-7, there is an aperture 74 formed in the planarsurface 67 of locking cap 60 that includes diametrically opposed flatsurfaces 76 corresponding to diametrically opposed longitudinal lands 78formed on the threaded portion 42 of the drive shaft 40. The interactionbetween the opposed surfaces 76 of aperture 74 and the opposed lands 78of threaded portion 42 allow axial movement of locking cap 60, relativeto the drive shaft 40, while preventing rotation of the locking cap 60relative to drive shaft 40, as locking cap 60 is moved into a lockingposition through rotation of lock nut 62.

Further, one or more alignment and/or engagement features can beprovided on the interspinous implant 10, for engaging an insertiondevice therefor. As illustrated in the embodiment of FIGS. 1-7, anannular recess 13, can be provided in the proximal region of the implant10 for securing the implant to an insertion device, limitingunintentional relative axial motion. In conjunction with the annularrecess 13, one or more axial, circumferentially outer grooves 16 can beprovided for limiting unintentional relative rotational movementtherebetween.

FIGS. 8-11 illustrate example aspects of insertion of devices inaccordance with the invention, and are described in connection with theinterspinous implant of FIGS. 1-7. As seen in FIG. 8, a sleeve 87 isprovided to facilitate insertion. The insertion methods can include useof a stylet, dilators, and the like to gain access and define a path forthe sleeve 87, as will be described in more detail below. However,dorsal insertion can be accomplished as set forth in U.S. patentapplication Ser. No. 12/011,905, filed Jan. 30, 2008 (U.S. Pub. No.2009/0054988), which is incorporated herein by reference in itsentirety.

As illustrated, in FIG. 8, dorsal insertion of the subject implants,represented by implant 10, can be effected by forming an incision 89through the skin 88 of a patient, at a level corresponding to a targetinterspinous process space 82, defined between adjacent vertebralprocesses 81 a, 81 b. With dorsal entry illustrated in FIG. 8, the pathtraversed by the implant 10, and therefore also by the sleeve 87 iscurved to align the path and the implant 10 with the target interspinousprocess space 82.

FIG. 9, in contrast, illustrates direct lateral insertion of the implant10 into the target interspinous process space 82. In this arrangement,an incision 99 is formed in the skin 88 of a patient, and ultimately asleeve 97 is advanced through the tissue to the target interspinousprocess space 82, through which the implant 10 is advanced, connected tothe insertion device 92. As shown in FIGS. 10 and 11, which areillustrated for clarity without the sleeve 97, the insert 10 is axiallyrotated by way of the insertion device 92, thus threading the implant 10into the target interspinous process space 82, distracting the adjacentspinous processes 81 a, 81 b, and advancing the implant into its finalposition, generally centered with respect to the spinous processes 81 a,81 b. During the rotation of the implant 10, relative rotation and axialtranslation between the implant 10 and the insertion device 92 ispreferably inhibited by the above-mentioned grooves 13, 16. When inposition, the engagement arms 22 a, 22 b can be actuated into thedeployed configuration shown in FIG. 11. Subsequently, the lock nut 62can be tightened, advancing the locking cap 60 distally into engagementwith the body 12, thus rotationally engaging the locking cap 60 with thebody 12 by way of the toothed surface 70 and ribs 68 a-68 d, describedhereinabove. Moreover, the lock nut 62 maintains frictional engagementwith the locking cap 60, to axially and rotationally secure the lock nut62 and locking cap 60. Subsequently, one or more osteogenesis promotingsubstances can be packed in and/or around the implant 10 to promotespinal fusion, if desired.

The set pins 64 a and 64 d, are provided in the illustrated embodimentfor maintaining an axial connection (with respect to a centrallongitudinal axis of the implant), keeping the locking cap 60 and locknut 62 together, while permitting axial rotation of the lock nut 62,with respect to the locking cap 60. Accordingly, tightening of the locknut 62 causes rotational locking engagement between the body 12, lockingcap 60 and the drive shaft 40, fixing the position of the engagementarms 22 a, 22 b. Similarly, loosening of the lock nut 62 pulls thelocking cap 60 proximally by way of the set pins 64 a and 64 d,permitting unlocking and retraction of the engagement arms 22 a, 22 b topermit removal of the implant 10.

A separate tap can be used before the insertion of the implant, or theimplant can be provided with features that provide self-tappingcapability, as described herein.

As discussed above, methods of lateral insertion of the spinal implant10 into a target interspinous process space 82 can include, followingforming the incision 99, inserting a stylet (not illustrated) throughthe incision, laterally to the target interspinous process space 82,preferably using an internal imaging technique, such as fluoroscopy.Insertion of the stylet forms an entry path, along which one or moredilators can be sequentially advanced, in order to dilate soft tissuesbetween the incision and the target interspinous process space 82. Thesleeve 97 can then be advanced through the entry path. Followingselection of an implant 10 having a size appropriate for a desiredamount of interspinous distraction, the implant 10 can be inserted, heldby the insertion device 92, advanced through the sleeve 97, up to thetarget interspinous process space 82, after which the implant can beinserted into the interspinous process space. In the case of threadedimplants, rotational motion is applied to advance the implant 10 anddistract the adjacent spinous processes 81 a, 81 b. In the case ofnon-threaded implants, laterally-directed pressure can be applied untilthe implant is in the desired position, after which any engagementelements, if provided, can be deployed.

FIGS. 12 and 13 are perspective views of a further embodiment of aninterspinous implant 100 in accordance with the invention, having anintegral tap chamfer 117 on a leading end 115 thereof, providingself-tapping capability, and thus eliminating a need to separately tap atarget interspinous process space (e.g. 82). Elements identical to thosedescribed in connection with above-described embodiments are indicatedwith the same reference numbers.

The implant 100 is similar in many respects to the implant 10 of FIGS.1-7, and includes a threaded body 112, claw portions 26 a, 26 b onrespective engagement arms, an optional detent 3, lock nut 62, endfitting 48 for actuation of the engagement arms, as described inconnection with the embodiment of FIGS. 1-7. In this embodiment,however, a proximal cap 119 is provided with the body 112, and ispreferably unitarily formed, such as by machining and/or casting from ametal material, such as titanium, a surgical grade stainless steel orother suitable biocompatible material, such as PEEK, for example. Theproximal cap 119 is configured to receive the proximal end of the body12, thereby maintaining the portions of the body, split longitudinally,in mutual contact. The proximal cap 119 is preferably press-fit on thebody during assembly thereof, but could be attached in another suitablemanner, which may include friction fit, mutual threaded engagement orthe like. The proximal cap 119 includes an annular toothed surface 70(see, for example, FIG. 15), which is a unitary embodiment of such afeature, provided in separate halves 70 a, 70 b in above-describedembodiments. The proximal cap 119 is also provided with opposedcircumferentially tangential grooves 113, in planar portions 137, alsoprovided on the proximal cap. The planar portions 137 and the grooves113, respectively prevent unintentional relative rotational and axialmovement between the implant 100 and an insertion device. The lockingcap 160 includes two circumferentially opposed ports 172, providedtherein.

FIGS. 14 and 15 are perspective and exploded perspective views of afurther embodiment of an interspinous implant 200 in accordance with theinvention, having a separately formed tip portion 205 and internal core207, which provide additional structural rigidity to the implant 200.Elements identical to those described in connection with above-describedembodiments are indicated with the same reference numbers. Many elementsare essentially the same as those of the foregoing embodiments, as isthe function of the engagement arms and their respective engagementclaws 26 a, 26 b. The proximal cap 119 is configured and functions likethat of the embodiment of FIGS. 12 and 13. The exploded view of FIG. 15illustrates one example configuration of a proximal end portion of thebody portions 12 a, 12 b, where they are engaged by the proximal cap119.

The implant 200 differs in that the tip portion 205, and integral core207 are provided, and in conjunction with the proximal cap 119, providea strong overall structure to the implant 200. The tip 205 and core 207are preferably formed of a relatively rigid material, such as a titaniumalloy, or alternatively of another suitable material. A pin 233 ispreferably provided for mutually engaging the distal portion of the bodyhalves 212 a, 212 b, the core 207 and tip 205, by way of an aperture 209therethrough. The pin 233 is secured in a suitable manner, such as witha clip 235, by laser welding or other suitable connection.

FIG. 16 is a perspective view of a further embodiment of an interspinousimplant 300 in accordance with the invention, having a body 312 with anouter surface, including leading surface 315 and tip 305, that are notthreaded. FIG. 17 is a rear (dorsal) view illustrating placement of theinterspinous implant 300, placed in a target interspinous process space82, and FIG. 18 is a partial exploded view of an alternative arrangementfor a distal tip portion for interspinous implants in accordance withthe invention. Elements identical to those described in connection withabove-described embodiments are indicated with the same referencenumbers.

As discussed above, advancement of the implant 300 differs from threadedimplants described herein, in that rotational movement does not advancethe implant into the target interspinous process space, and lateralforce must be applied instead.

The internal structure of the implant 300 can include a core, as withthe embodiment of FIGS. 14 and 15, and can be integral with the tip 305,or alternatively, the tip 305 can be separately formed and inserted intothe assembly of the implant 300. A proximal recess 3 can optionally beprovided to facilitate engagement with an insertion device, as describedabove.

While the devices and methods of the subject invention have been shownand described with reference to select preferred embodiments, thoseskilled in the art will readily appreciate that changes and/ormodifications may be made thereto without departing from the spirit andscope of the subject invention.

1. A spinal implant comprising: an elongated threaded body portiondimensioned and configured for percutaneous introduction into theinterspinous process space and having a longitudinal axis, the bodyportion including an interior cavity and a pair of deployable engagementmembers mounted to rotate in tandem about a common axis extendingtransverse to the longitudinal axis of the body portion between a stowedposition retracted within the interior cavity of the body portion and adeployed position extended from the interior cavity of the body portionfor engaging the spinous process, wherein each engagement memberincludes a pair of curved engagement arms extending radially outwardlyfrom a central hub and each engagement arm includes a distal clawportion having a plurality of teeth for engaging the spinous process. 2.A spinal implant as recited in claim 1, further comprising a driveassembly extending into the interior cavity of the threaded body portionfor selectively moving the engagement members in tandem from the stowedposition to the deployed position.
 3. A spinal implant as recited inclaim 2, further comprising means operatively associated with the driveassembly for selectively locking the engagement members in the deployedposition.
 4. A spinal implant as recited in claim 1, wherein the driveassembly includes a main drive shaft that extends into the interiorcavity of the body portion along the longitudinal axis of the bodyportion.
 5. A spinal implant as recited in claim 1, wherein the threadedbody portion includes an outer profile, tapering axially inwardly in adistal nose portion thereof, configured to gradually distract adjacentspinous processes during insertion of the implant into the interspinousprocess space.
 6. A spinal implant as recited in claim 5, whereinthreads are provided on the body portion, and extend at least partiallyover the nose portion thereof.
 7. A spinal implant as recited in claim6, wherein the distal nose portion tapers axially inwardly with respectto a central region of the body, by an angle of about 30 degrees, withrespect to a longitudinal axis thereof.
 8. A spinal implant as recitedin claim 1, further comprising an interior core portion adapted andconfigured for rigidifying the spinal implant.
 9. A spinal implant asrecited in claim 8, wherein the core portion includes an integral tipportion, arranged at the distal end of the implant.
 10. A spinal implantas recited in claim 1, wherein the body portion includes a separatelyformed proximal portion, formed of a material dissimilar from a materialfrom which a central portion of the body portion is formed.
 11. A spinalimplant as recited in claim 10, wherein the proximal portion is formedof a metal material, and the central portion of the body portion isformed of a polymeric material.
 12. A spinal implant as recited in claim1, wherein the teeth are dissimilar.
 13. A spinal implant comprising: a)A threaded elongated body portion dimensioned and configured forpercutaneous introduction into the interspinous process space, thethreaded elongated body portion defining a longitudinal axis and havingan interior cavity; b) a pair of deployable engagement members adaptedand configured to move in tandem about a common axis extendingtransverse to the longitudinal axis of the threaded elongated bodyportion between a stowed position retracted within the interior cavityof the threaded elongated body portion and a deployed position extendedfrom the interior cavity of the threaded elongated body portion forengaging the spinous process; and c) a rotatable drive shaft extendinginto the interior cavity of the threaded elongated body portion alongthe longitudinal axis thereof for selectively moving the engagementmembers in tandem from the stowed position to the deployed position,wherein two engagement members are provided for engaging spinousprocess, each engagement member includes a pair of curved engagementarms extending radially outwardly from a central hub, and eachengagement arm includes a distal claw portion having a plurality ofteeth for engaging the spinous process.
 14. A spinal implant as recitedin claim 13, a locking cap operatively associated with the rotatabledrive shaft and the body portion for selectively locking the engagementmembers in the deployed position.
 15. A spinal implant as recited inclaim 13, wherein the teeth are dissimilar.
 16. A method of lateralinsertion of a spinal implant into an interspinous process space,comprising the steps of: a) forming an incision in a patient's skin,lateral from a target interspinous process space, in which the implantis to be placed; b) inserting a stylet through the incision, laterallyto the target interspinous process space, using an internal imagingtechnique, to form an entry path; c) inserting one or more dilators,sequentially, along the entry path to dilate soft tissues between theincision and the target interspinous process space; d) inserting asleeve through the entry path; e) selecting an implant having a sizeappropriate for a desired amount of interspinous distraction and a pairof deployable engagement members for engaging the spinous process, theengagement members being mounted for rotational deployment in tandemabout a common axis that extends transverse to a longitudinal axis ofthe implant, wherein each engagement member includes a pair of curvedengagement arms extending radially outwardly from a central hub, andeach engagement arm includes a distal claw portion having a plurality ofteeth for engaging the spinous process; f) inserting the implant, heldby an insertion device, through the sleeve, up to the targetinterspinous process space; g) advancing the implant into theinterspinous process space; and h) deploying the pair of engagementmembers.
 17. A method of lateral insertion of a spinal implant into aninterspinous process space of claim 16, wherein the advancing stepincludes rotating the implant along a longitudinal axis thereof, toeffect axial advancement of the implant by way of threads formed on anouter surface thereof.
 18. A method of lateral insertion of a spinalimplant into an interspinous process space of claim 16, wherein theteeth are dissimilar.